Ebright: Infectious Diseases of the GI Tract

Question 1

Mild diarrhea definition:

Answer 1

Production of up to 3 loose stools per day without abdominal or systemic symptoms.

Question 2

Moderate to severe diarrhea definition:
Local symptoms:
Systemic symptoms:

Answer 2

4 or more loose stools per day, often associated with other symptoms

Local symptoms: abdominal cramps, N/V, or tenesmus (painful defecation)

Systemic symptoms: fever, malaise, or dehydration

Question 3

Diarrhea worldwide:

Answer 3

Second leading cause of death behind acute respiratory infections

Major death toll in children

Question 4

What bacteria cause GI disease? (9)

Answer 4

Shigella
Salmonella
E.coli
Campylobacter
Yersinia
Vibrio cholera
Clostridium difficile
Aeromonas hydrophila
Bacillus cereus

Question 5

What protozoa cause GI disease? (6)

Answer 5

Giardia lamblia
Cryptosporidia
Entameoba histolytica
Isospora belli
Cyclospora
Microsporidia

Question 6

What viruses cause GI disease? (4)

Answer 6

Rotavirus
Adenovirus (serotypes 40 and 41)
Calcivirus (Norovirus)
Astrovirus

Question 7

What fungus causes GI disease? (1)

Answer 7

Candida (?)

Question 8

What is the mechanism of disease production for the majority of diarrhea?

Answer 8

Non-Inflammatory

Basics: majority of diarrhea; usually involves small intestine

Question 9

Non-Inflammatory

Diarrhea may result from overproduction of enterotoxin from what organisms (4):

Answer 9

Vibrio cholera

ETEC

Bacillus cereus

Clostrium perfrigens

Question 10

Non-Inflammatory

Diarrhea may result from other processes that alter absorptive function of villus tip due to what organisms (5):

Answer 10

EPEC
Cryptosporidium
Giardia
Rotavirus
Norovirus

Question 11

Inflammatory

Basics:

Answer 11

Often involves invasion of GI mucosa and/or production of cytotoxin; usually involves the colon

Question 12

Inflammatory

Examples:

Answer 12

Shigella
Salmonella
Campylobacter
Clostridium difficile (cytotoxn)
Entamoeba histolytica

Question 13

What causes Bacteremia and Systemic Infection? (3)

Answer 13

Enteric fever (typhoid)

Non-typhoid salmonella bacteremia

Shigella, campylobacter and listeria can all cause bacteremia (less common)

Question 14

Classification of GI disease by Clinical Presentation

Emphasis on N/V rather than diarrhea; absent or low grade fever; upper abdominal symptoms (3)

Answer 14

Staphylococcus aureus (preformed enterotoxin in food)

Bacillus cereus (emetic form; preformed enterotoxin in food)

Heavy metal food poisoning

Question 15

Classification of GI disease by Clinical Presentation

Emphasis of N/V and large volume diarrhea (watery); absent or low grade fever); small intestine disease (8)

Answer 15

o	Vibrio cholera
o	ETEC
o	Bacillus cereus (diarrheal form)
o	Clostridium perfringens
o	Giardia lamblia
o	Rotavirus
o	Norovirus
o	Cryptosporidium

Question 16

Classification of GI disease by Clinical Presentation

Emphasis on lower intestinal (colon) symptoms; smaller volume frequent stools with blood and leukocytes; tenesmus, fever, abdominal cramps (6)

Answer 16

o	Shigella
o	Salmonella (colonic form)
o	Campylobacter
o	Non-cholera vibrios (ie. V.parahemolyticus)
o	EIEC
o	Entamoeba histolytica

Question 17

Classification of GI disease by Clinical Presentation

Emphasis on systemic illness with toxicity, prostration, high fever; diarrhea may be absent (2)

Answer 17

o Enteric fever (Samonella typhi)

o Non-typhoid salmonella bacteremias

Question 18

By Social Setting/Underlying Immune Status of Host

Hospital Acquired (Nosocomial): (2)

Answer 18

o	Clostridium difficile
o	Rotavirus (especially in young children)

Question 19

By Social Setting/Underlying Immune Status of Host

Day Care: (4)

Answer 19

o Shigella
o Rotavirus
o Giardia
o Cryptosporidium

.

Question 20

By Social Setting/Underlying Immune Status of Host

Traveler’s Diarrhea: (4)

Answer 20

o ETEC
o Giardia
o Salmonella
o Shigella

Question 21

By Social Setting/Underlying Immune Status of Host

Food Borne: (6)

Answer 21

o	Norovirus (majority) 
o	Other bacterial causes include Salmonella, Campylobacter, E.coli, Clostridium perfringens, and Shigella

Question 22

By Social Setting/Underlying Immune Status of Host

Water Borne: (6)

Answer 22

o	Giardia
o	Cryptosporidium
o	E.coli
o	Salmonella
o	Campylobacter
o	Norovirus

Question 23

By Social Setting/Underlying Immune Status of Host

Patients with AIDS: (5
Natalja’s)

Answer 23

Increased risk for any type of infection

Special risks also associated with AIDS patients who are immunocompromised: Mycobacterium avium, Cryptosporidium, Cyclospora, Giardia, Microsporidia

Question 24

Enteropathogenic E.coli (EPEC)

Common Presentation:
Pathogenesis:
Diagnosis:

Answer 24

Common Presentation: epidemic infantile diarrhea (ie. hospital nursery outbreaks), especially in developing countries

Pathogenesis: adhere to and efface the brush border of the small intestine

Diagnosis: not available in a routine lab

Question 25

Enterohemorrhagic E.coli (EHEC) Most common cause: Produces: Pathogenesis is similar to:

Answer 25

Cause: most commonly O157:H7 serotype that produces Shiga toxin (not the only one that produces this); often associated with undercooked ground beef Pathogenesis: similar to EPEC, but with the presence of Shiga toxin (toxic to epithelial and endothelial cells)

Question 26

Enterohemorrhagic E.coli (EHEC) Presentation: Diagnosis: What do antibiotics cause?

Answer 26

Presentation: severe abdominal cramps, bloody diarrhea; may or may not have fever and fecal leukocytes Diagnosis: SMAC growth will be sorbitol negative Antibiotics are NOT effective: can also promote hemolytic uremic syndrome

Question 27

What is the most common cause of acute bacterial diarrhea worldwide (especially traveler’s and children under 2)

Answer 27

Enterotoxigenic E.coli (ETEC)

Question 28

Enterotoxigenic E.coli (ETEC) Transmission: Toxins: What is similar to cholera? What does it result in?

Answer 28

Transmission: most commonly via contaminated food Toxins: plasmid mediated enterotoxin (heat labile and heat stable) - Heat Labile: similar to cholera (activates adenylate cyclase to increase cAMP); results in chloride and water secretion

Question 29

Enterotoxigenic E.coli (ETEC) Presentation: Diagnosis: Treatment:

Answer 29

Presentation: large volume watery diarrhea Diagnosis: not available in routine lab Treatment: trimethoprim-sulfa or ciprofloxacin

Question 30

Enteroinvasive E.coli (EIEC) Presentation: Similar to: Diagnosis:

Answer 30

Presentation: uncommon outbreaks of dysentery in adults, often transmitted by food Similar to Shigella: invasiveness Diagnosis: not available in routine lab

Question 31

Enteroaggregative E.coli (EAEC) “Stacked brick” adherence to: Recently identified as a cause for: (3)

Answer 31

“Stacked brick” adherence to Hep-2 cells Recently identified as a cause for: o Traveler’s diarrhea o Persistent childhood diarrhea in developing countries o Chronic diarrhea in AIDS patients

Question 32

Salmonella Taxonomy Most common types in the US: What type frequently causes bacteremia?

Answer 32

S.enteritidis and S.typimurium: most common in US S.choleraesuis: frequently causes bacteremia

Question 33

Salmonella Taxonomy What type is widely distributed in animal kingdom? What has only humans as hosts?

Answer 33

Non-typhi Salmonella: widely distributed in animal kingdom S.typhi and S.paratyphi: only human hosts

Question 34

Salmonella Transmission: Diagnosis:

Answer 34

Transmission: Via contaminated food and water Diagnosis: culture of stool or blood

Question 35

Salmonella Clinical Presentations (3):

Answer 35

Gastroenteritis Enteric fever (typhoid) Extra-intestinal infection

Question 36

Salmonella Treatment: In the case of gastroenteritis:

Answer 36

Antibiotics for enteric fever and extra-intestinal infections (not usually given for gastroenteritis unless it is an extreme case- age, immunocompromised, AIDS, sickle cell)

Question 37

Shigella Types: (4)

Answer 37

Taxonomy: S.dysenteriae, boydii, flexneri and sonnei

Question 38

Shigella Most common type in the US: AIDS patients:

Answer 38

S.sonnei: most common in the US S.flexneri: most common in AIDS patients

Question 39

Shigella What does type 1 S.dysenteriae produce? S.dysenteriae complications: (5)

Answer 39

S.dysenteriae: type 1 produces Shiga toxin (cytotoxin) Complications: hemolytic uremic syndrome (HUS), toxic megacolon, encephalopathy, seizures, reactive arthritis

Question 40

Shigella Diagnosis: Treatment:

Answer 40

Diagnosis: by stool culture (bacteremia is rare therefore blood cultures will be negative) Treatment: antibiotics given in moderate to severe illness (shortens course and reduces transmission)

Question 41

Cholera Epidemic cholera is caused by what types? Transmission: Disease is mediated by:

Answer 41

Epidemic cholera: Vibrio cholera 01 and 0139 Transmission: contaminated water or food, or poorly cooked shellfish Disease: Classic non-inflammatory diarrhea mediated by enterotoxin (choleragen)

Question 42

Cholera Pathogenesis: Diagnosis: Treatment:

Answer 42

Pathogenesis: patients due from dehydration and electrolyte loss Diagnosis: can be made in most labs by stool culture HOWEVER, most labs in the US don’t test for it (because it is uncommon) unless instructed to Treatment: aggressive rehydration and antibiotics to shorten the illness (tetracycline or azithromycin)

Question 43

What is the most frequent cause of bacterial enteritis in developed countries?

Answer 43

Campylobacter

Question 44

Campylobacter Transmission: Symptoms:

Answer 44

Transmission: often from handling and consuming poultry Symptoms: diarrhea and severe cramping abdominal pain

Question 45

Campylobacter What is a possible sequelae post-infection?

Answer 45

Guillan Barre Syndrome

Question 46

Campylobacter Diagnosis: Treatment:

Answer 46

Diagnosis: can be made in most labs using microaerophilic atmosphere and 42 degrees C Treatment: erythromycin given to those with marked symptoms or immunocompromised; resistance to quinolones is increasing

Question 47

Clostridium difficile Common cause of what? Symptoms: What can colitis form?

Answer 47

Common cause of hospital-acquired diarrhea: due to preceding antibiotic use (predisposes colon to overgrowth) Symptoms: inflammatory colitis and diarrhea - Colitis can be severe: with formation of pseudomembranes

Question 48

Clostridium difficile Diagnosis: Treatment:

Answer 48

Diagnosis: tissue-culture assay or EIA/PCR on stool sample Treatment: oral metronidazole or vancomycin

Question 49

What is the most common cause of acute gastroenteritis and food poisoning in the US?

Answer 49

Norovirus

Question 50

Norovirus Symptoms: Diagnosis: Treatment:

Answer 50

Symptoms: illness usually lasts 1-2 days with N/V/D Diagnosis: using immune electron microscopy, RT-PCR (only available in reference labs such as CDC and state health departments) No specific treatment

Question 51

What is the most common cause of severe diarrhea in children?

Answer 51

Rotavirus - Both in developed and developing countries

Question 52

Rotavirus Common age groups: Adults: Genome type:

Answer 52

Common age groups: 6-24 months Adults: have symptoms less often dsRNA

Question 53

Rotavirus Symptoms: Seasonal: Transmission:

Answer 53

Symptoms: N/V/D lasting 4-8 days Seasonal: most common during the winter (sporadic rather than epidemic) Transmission: fecal-oral (person to person)

Question 54

Rotavirus Diagnosis: Vaccine: Treatment:

Answer 54

Diagnosis: analyze stool sample via immune electron microscopy or ELISA (can be done in most labs) Vaccines: 2 new live, oral vaccines given during childhood No specific treatment

Question 55

What is the most commonly reported parasitic disease in the US?

Answer 55

Giardia lambia

Question 56

Giardia lambia Transmission: Where does it inhabit?

Answer 56

Transmission: fecal-oral and contaminated food or water Pathogenesis: inhabits upper small bowel, but does not invade the mucosa

Question 57

Giardia lambia Lasts how long? Symptoms: Diagnosis:

Answer 57

Symptoms: usually last 5-7 days (after a 1-3 week incubation period); also often causes prolonged illness and diarrhea Diagnosis: stool exam for cysts, small bowel biopsy, string test, or ELISA test to detect stool antigen

Question 58

Giardia lambia Treatment: (3)

Answer 58

Treatment: metronidazole, furazolidone, or quinacrine

Question 59

RECOMMENDATIONS FOR COST-EFFECTIVE TESTING FOR ENTERIC PATHOGENS: Routine Cultures should always include: (3) Use up to 2 stool samples for what?

Answer 59

Routine Cultures should always include: - Campylobacter, Salmonella, Shigella - Other agents based on in-house or regional survey data • Submit additional samples for less common bacteriologic agents: second-line test after common agents have been ruled out Up to 2 stool samples for ova and parasite examination: can forego this testing with the emergence of specific tests for Giardia, Entamoeba histolytica and Cryptosporidium if these are the more likely causative agents

Question 60

RECOMMENDATIONS FOR COST-EFFECTIVE TESTING FOR ENTERIC PATHOGENS: How many stool samples to rule out C.difficle? Use 3-day rule for what?

Answer 60

2-3 samples to rule out Clostridium difficile: samples should be spaced several days apart Use 3-day rule for all stool and parasite testing (in general, do not order after 3rd day of hospitalization)